A cost-benefit analysis of medical videotape teaching is reported. Two colour videotapes, used in teaching a segment of tropical paediatrics, have been prepared for this study, using a minimum budget, but with accurate costing. Anonymous appraisal forms have been used to quantify perceived benefit. Current minimum costs for a completed standard half-hour teaching tape are $48 per minute, or $31 per minute if the medical producer's time is not costed. Perceived worth by consumers (audience of medical subjects either undergraduate or postgraduate) does not exceed a median of $2 per subject per teaching tape. (The basic cost reference unit, a loaf of bread, cost 50 cents at the time of this study). These current estimates indicate that a medical videotape has to be shown to over 2,000 students to justify expense; if programmes become obsolete within three years, then a tape must be shown to at least 800 students a year, to justify expenses. Indiscriminate use of videotapes should be tempered by anonymous consumer appraisal studies, especially where producers are teaching captive audiences.